1. Field of the Invention
This invention concerns a thread-wound golf ball with a high impact resiliency and the ability to increase flying distance.
2. Description of the Prior Art
Heretofore, one-piece golf balls, two-piece golf balls, thread-wound golf balls or the like have been known, and various attempts have been made to improve the performance of the balls in order to increase flying distance.
Among them, the thread-wound golf ball comprises a solid or liquid ball core, a plurality of highly elastic rubber thread layers tightly wound therearound and an outer skin layer or cover. Of the constituent elements, the rubber thread layer gives a most significant effect for improving the impact resiliency to increase the flying distance of the golf ball. In view of the above, it is desired to increase the impact resiliency of rubber thread constituting the rubber thread layer in order to increase the flying distance of the golf ball. As a method of increasing the impact resiliency of the rubber thread layer, polyisoprene rubber or polyisoprene rubber which has a cis-content of 90-94% has been used for the rubber thread to decrease the energy loss upon great stretching of the rubber thread, thereby increasing the impact resiliency of the golf ball. However, the method of using the polyisoprene rubber or the polyisoprene rubber which has a cis-content of 90-94% in the rubber thread involves problems wherein workability upon manufacture of the golf ball is worsened and the productivity is reduced, accompanied with the decrease in energy loss and, accordingly, some improvement has been desired therefor.
Further, in order to improve the impact resiliency for obtaining increased flying distance of the golf ball, it is desired to improve the impact resiliency and destructive strength of material constituting the ball core. While cis-polybutadiene, cis-polyisoprene or a mixture thereof has been used for the ball core, none of them can provide sufficient impact resiliency and destructive strength and an improvement is also required therefor.